This invention relates to the treatment of contaminated groundwater, particularly to remediation of groundwater contaminants with halogenated solvents, and more particularly to a system for such remediation of groundwater contaminants based on catalytic reduction reactions within reactive well bores.
Contamination of groundwater resources by halogenated solvents and metals poses a significant environmental problem. Existing conventional groundwater cleanup technologies suffer from a number of disadvantages, including the need to construct surface facilities and pipelines, and the need to deploy different technologies to treat different contaminants. One particular problem of concern is that many conventional treatment technologies merely transfer the contaminant from one medium (water) to another (e.g., activated carbon), thus producing a secondary waste stream. Recently, see U.S. Pat. No. 5,332,496 issued Jul. 26, 1994, to F. Rasouli, et al., a treatment technology has been developed involving catalytic reduction dehalogination by hydrogen with a palladium catalyst in a system located above the ground surface.
The present invention addresses the above mentioned problems, and provides a compact and versatile groundwater treatment system based on chemical reduction processes for deployment within the borehole of reactive treatment wells, and the boreholes may be pre-existing. This system has a minimal surface footprint and enables the destruction of a broad suite of contaminants without generating secondary waste streams. The treated groundwater and the harmless species produced by the catalytic reduction reactions are reinjected into an adjacent water-bearing zone. The treatment uses dissolved hydrogen as a reducing agent in the presence of a metal catalyst such as palladium.
It is an object of the present invention to provide catalytic destruction of groundwater contaminants in reactive extraction wells.
A further object of the invention is to provide treatment of contaminated groundwater without producing secondary waste streams.
A further object of the invention is to provide a system for treatment of contaminated groundwater, wherein the treatment process is within well bores thus significantly reducing the surface facilities and costs associated therewith.
Another object of the invention is to provide a system for remediating groundwater contaminated with halogenated solvents, certain metals, and other inorganic species based on catalytic reduction reactions within reactive well bores.
Another object of the invention is to provide contaminated groundwater treatment using dissolved hydrogen as a reducing agent in the presence of a metal catalyst, such as palladium, to reduce halogenated solvents (or other organic compounds) to harmless species, such as ethane or methane, and immobilize certain metals in lower valence states.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawing. The present invention involves a system for rapidly destroying chlorinated hydrocarbon contaminants that are dissolved in groundwater by catalyic reduction dehalogenation (CRD). CRD involves dissolved hydrogen as a reducing agent, in the presence of a palladium-on-alumina catalyst, for example. It is chemically transforms compounds such as Trichlovoethene (TCE) and tetrachloroethene (PCE) into environmentally-benign ethane without the accumulation of intermediate transformation products, such as vinyl chloride. The rapid reduction reactions allow the design of a reactor unit that is compact enough to be placed within a well bore. Using a dual-screen well configuration, contaminated water may be extracted from one portion of the subsurface, treated by a CRD reactor within a well bore, and then re-injected into another water-bearing zone. This CRD/reactive well system may be used to remediate contaminated groundwater in instances where treatment in surface facilities may be otherwise undesirable. The system may also be utilized for certain metals and other inorganic species, wherein the metals are reduced to lower valence states, and the other inorganic species reduced to harmless species.